Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751771AbdFTS7c (ORCPT ); Tue, 20 Jun 2017 14:59:32 -0400 Received: from b.ns.miles-group.at ([95.130.255.144]:44724 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751025AbdFTS7b (ORCPT ); Tue, 20 Jun 2017 14:59:31 -0400 Subject: Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU From: Richard Weinberger To: Yu-cheng Yu Cc: Thomas Meyer , elicooper@gmx.com, linux-kernel@vger.kernel.org, "open list:USER-MODE LINUX (UML)" , linux-x86_64@vger.kernel.org, Dave Hansen , Ingo Molnar References: <1497923806.7300.2.camel@m3y3r.de> <98803c66-4a36-a95f-5a1b-51a40de7a3e6@nod.at> <1497948550.7300.5.camel@m3y3r.de> <25066617-df15-6d21-713c-1ede1e953448@nod.at> <1497981874.22112.20.camel@test-lenovo> <4d431238-28c7-3680-42f2-f7cf32acbc86@nod.at> Message-ID: <2fc7383c-852a-be3c-f934-b125fe9bdba2@nod.at> Date: Tue, 20 Jun 2017 20:59:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <4d431238-28c7-3680-42f2-f7cf32acbc86@nod.at> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1029 Lines: 33 Yu-cheng, Am 20.06.2017 um 20:17 schrieb Richard Weinberger: > Yu-cheng, > > Am 20.06.2017 um 20:04 schrieb Yu-cheng Yu: >>>> So to summarize: >>>> >>>> - PTRACE_GETREGSET with NT_X86_XSTATE gets 832 and return 832, with no >>>> error. >>>> >>>> - PTRACE_SETREGSET get 832 (sizeof struct _xstate) but wants at least >>>> 1088, otherwise it will fail with -EFAULT (why not -EINVAL?) >>>> >>>> Ideas? >> >> We considered allowing a partial XSAVE buffer for PTRACE_SETREGSET, but >> it was that the XSAVE instruction requires a full-size buffer led to >> this choice. Using a smaller buffer for XSAVE causes a fault. > > So, this code is not supposed to work? > > iov.iov_base = fp_regs; > iov.iov_len = sizeof(struct _xstate); > ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov); > ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov); > > This is what UML does and on Thomas's new Laptop PTRACE_SETREGSET is failing. Hmm, I think we need to do what gdb does, it uses a buffer of size X86_XSTATE_MAX_SIZE. Thanks, //richard